Electric incandescent projector lamp with heat shield



Sept. 19, 1967 5. H. BURNETT ETAL 3,343,021

ELECTRIC INCANDESCENT PROJECTOR LAMP WITH HEAT SHIELD Filed Dec. 28, 1964 Irv/an hors: George fiBur'ne t t Emma-ti k HW'ILeL Their A i: OTTWEH United States Patent Office 3,343,621 Patented Sept. 19, 1967 3,343,021 ELECTRIC INCANDESCENT PROJECTOR LAMP WITH HEAT SHIELD George H. Burnett, Cleveland Heights, and Emmett H. Wiley, Chesterland, Ohio, assignors to General Electric Company, a corporation of New York Filed Dec. 28, 1964, Ser. No. 421,498 3 Claims. (Cl. 313--42) ABSTRACT OF THE DISCLQSURE In a compact, high intensity sealed beam type projection lamp having, in normal operation, a vertically disposed high intensity filament close to the reflector apex and mounted on leads extending through openings located in the glass reflector section of the bulb above and below the reflector axis, the upward flow of hot viscous gas around the filament is prevented from pocketing in the upper lead wire opening by providing a heat deflecting shield which is supported by the said upper lead and extends vertically in front of said opening and between said opening and the filament.

This invention relates generally to electric incandescent lamps, and more particularly to high intensity projection lamps of the so-called sealed beam type comprising a pressed glass reflector section and a glass cover or lens section.

In lamps of this type, the filament is supported by lead wires which extend through openings adjacent the apex of the reflector section and are anchored in metal terminal thimbles which have their edges fused and embedded in the glass around the margin of said openings. In certain compact, high intensity lamps of this type, for example, lamps having filaments of 650 watts rating at 240 volts in a bulb of a size designated in the art as PAR 36, having a maximum diameter at its periphery of about 4 /2 inches, difliculties have been experienced in the area of one or more of the said lead wire openings and its associated thimble. It has been found that overheating at said area occurs due to the action of an extremely hot and viscous flow of gaseous convection currents upwardly around the filament and circulating to the said lead wire opening, together with radiant energy projected directly toward said opening from the filament, additional heat conducted into the opening along the associated lead wire, and further radiant energy reflected back toward said opening from the conventional curved cover glass, all resulting in absorption and pocketing of heat in the vicinity of said opening and the associated thimble. Such overheating can result in melting and destruction of the reflecting coating, usually of aluminum, on the inner surface of the reflector section around said opening, distortion of the glass at the margin of said opening, and cracking of the hermetic seal between said glass and the rim of the associated thimble.

It is the principal object of this invention to provide means to overcome the aforesaid overheating in the vicinity of a lead wire opening and its destructive effects.

Having determined the cause of the difficulty, applicants have found that the object can be achieved by the provision of suitable heat-deflecting shield means at the front of the said lead wire opening and between the filament and said opening whereby to break up and divert most of the hot convection currents away from the said opening and to intercept radiant energy directed toward said opening from the filament.

Further features and advantages of the invention will appear from the following detailed description of a species thereof and from the drawing wherein:

FIG. 1 is an elevation, in section, of a lamp construction embodying the invention, the section being taken along the line I-I of FIG. 2 which is a fragmentary front elevation of the lamp broken away through the reflector section around its apex.

Referring to FIG. 1 of the drawing, the lamp comprises a sealed gas-filled bulb comprising a reflector section 1 of pressed glass and a pressed cover glass or lens section 2 fused together at their peripheries, the reflect/or section 1 being provided on its inner surface with a reflecting coating 3 which may be of aluminum or silver, for example. The reflector section 1 is preferably of generally paraboloidal contour with a horizontal axis indicated by the broken line 4. In a two-filament, dual beam lamp, as illustrated herein, the said reflector section 1 is provided with three lead wire openings 5, 6 and 7 (FIG. 2) arranged about its apex and its axis 4 to be approximately at the corners of a triangle, which may be an isosceles triangle, with the first and second openings 5 and 6 respectively, at opposite sides of said apex and axis 4 and in a horizontal plane including said axis 4, and the third opening 7 (FIGS. 1 and 2) above said horizontal plane and preferably in a vertical plane including said axis 4. Each of the openings 5, 6 and 7 is closed by a metal thimble 8, 9 and 10 respectively, havin a feathered edge hermetically sealed and embedded in the glass around the margin of the respective openings.

Three lead wires 11, 12 and 13 have their outer ends anchored in respective thimbles 8, 9 and 10, preferably by a quantity of brazing material 14 therein, and they project through respective associated openings 5, 6 and 7 into the interior of the reflector section 1, preferably parallel to each other and to the reflector axis 4. The first lead wire 11 includes a fuse section (not shown) adjacent its outer end, with a rigid insulating sleeve 16, preferably of ceramic material, spanning said fuse section and closely fitting the sections of the lead wire 11 interrupted by the fuse. The sleeve restores rigidity to the lead wire 11 which would otherwise flex rather readily at the fuse section which is of relatively smaller and more flexible wire or alloy as is well known in the art.

An auxiliary fourth lead wire 17 (FIG. 2) is connected, preferably by Welding, at one end to the first lead wire 11 and extends laterally therefrom to the vertical plane including the reflector axis 4 and to a point below the horizontal plane including said axis 4 with its free end 17a (FIG. 1) extending parallel to said axis 4 and in alignment with the third lead wire 13. The said fourth lead wire 17 is preferably welded to the first lead wire 11 at a point to engage one end of the ceramic sleeve 16 to thereby firmly confine said sleeve between the said wire 17 and the body of brazing material 14 in thimble 8.

A first helically coiled, preferably coiled-coil, filament 18 of tungsten wire extends horizontally between and is connected to the first and second lead wires 11 and 12 and is preferably substantially centered about the focus of the reflector section 1 on the axis 4. A second helically coiled, preferably coiled-coil, filament 19 extends vertically between and is connected to the third lead wire 13 and to the free end 17a of the auxiliary fourth lead wire 17; said filament 19 being located behind the filament 18 and behind the focus of the reflector section 1.

The mount assembly is made more rigid by an insulating glass bridge member 20 which extends laterally between and is secured at one end to the second lead wire 12 and at its other end to the auxiliary fourth lead wire 17 adjacent its free end. The glass bridge 20 is perferably secured to the respective lead wires by pairs of Wire studs 21 and 22 each having one end embedded in the bridge 20 and their other ends welded to the respective lead wires. The lead wire 17 is thereby firmly supported, and the lead wire 11 additionally supported, particularly against torsional weakness of the fuse section in lead wire 11, by virtue of the bridge connection 20.

The filaments 18 and 19 are also additionally supported by auxiliary support wires 23 and 24 respectively. Each said support wire 23 and 24 has one end embedded in the glass bridge 20 and has its free end formed to engage and support the respective filament 18 or 19 at its midpoint, preferably by a hook portion formed at the extremity of the lead wire. The support wire 23 extends generally parallel to the reflector axis 4 and then laterally to the midpoint of filament 18. The support wire 24 extends angularly toward the midpoint of filament 19. It will be noted that support wire 23 is anchored adjacent the end of bridge 20 near the second lead wire 12 carrying the filament 18 which is supported by said wire 23; and the support wire 24 is anchored adjacent the end of said bridge 20 near the fourth lead wire 17 which carries the filament 19 which is supported by said wire 24. Thereby, the said filament supports 23 and 24 are located in positions of lowest voltage potential, and arcing over between the supports, the filaments and the lead wires is avoided.

In a particular lamp of the type illustrated herein, the coiled-coil filaments 1S and 19 may be so designed that each consumes 650 watts. Thereby, a concentrated spot beam is provided by the filament 18 which is at the focus of the reflector section 1, whereas energization of the filament 19 provides a spreading flood beam because of its location behind the reflector focal point. It will be evident that, if desired, the reflector contour and the location of the filaments may be such that one of the filaments is located at the focal point and the other is located in front of the focal point rather than behind it.

The bulb 1, 2 is evacuated and gas-filled with an inert gas such as nitrogen, for example, in conventional manner through an aperture 25 at the apex and an exhaust tube extending therefrom, the sealed or tipped-off residue of the exhaust tube being shown at 26 (FIG. 1).

The particular filament supporting structure thus far described is not per se the subject matter of the present invention, but is separately disclosed and claimed in application Serial No. 421,499 of George H. Burnett, filed of even date herewith and assigned to the same assignee as the present invention.

During the operation of the lamp in the position shown in FIG. 1, the area in the vicinity of the upper lead wire opening 7 and thimble is subject to damage, particularly when the vertical filament 19 is energized. In accordance with the present invention, the difiiculty is obviated by providing a heat deflector or shield 27 at the front of the opening 7 and between said opening and the filament 19. Said shield 27 may be made of closely woven wire cloth or screen, but preferably of an imperforate sheet of refractory metal such as nickel or molybdenum. The shield 27 is preferably supported by the upper lead wire 13 which extends through a hole in the shield which may be provided with a narrow lateral flange portion 28 welded to said wire 13. Said shield 27 extends transversely of the reflector axis 4 to be in a vertical plane transverse to said axis 4.

The shield 27 preferably terminates at its lower end at the reflector axis 4 and exhaust opening 25; this is so that during processing of the lamp-a metal tube may be inserted through the exhaust tube 26 and opening 25 through which an inert gas is flushed into the bulb 1, 2 to avoid oxidizing the filaments and other metal parts, particularly during fusion sealing together of thebulb sections 1 and 2 at their peripheries. Nevertheless, the shield 27 is in a position to intercept radiant energy directed from the filament 19 toward the area of the opening 7, and to break up and divert away from said opening 7 the reflector section and a light-transmitting glass cover sec- 1 tion and adapted to be operated with the reflector axis horizontal, said reflector section having at least two lead hot gaseous convection currents arising around the said filament 19 so as to avoid the destructive consequences referred to above.

It will be evident that a conventional type of antiblackening grid or shield arranged ina horizontal plane above the filament 19 and in the pathof the convection currents arising therefrom, would not solve the problem; in fact, it would exaggerate the situation by deflecting some of the hot convection currents toward the opening 7.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electric incandescent projector lamp comprising a sealed gas-filled bulb including a compact concave glass wire openings adjacent its apex with one of said openings above said reflector axis substantially in a vertical plane including said axis, metal thimble members at the exterior of said reflector section closing respective said openings and having their edges fused in the glass around the margins of said openings, lead wires having their outer ends anchored in respective said thimbles and extending through the associated said openings into the interior of said reflector section, a high intensity helically coiled filament in said bulb electrically connected to and supported from said lead wires to extend vertically substantially in said vertical plane including said reflector axis and relatively close to said reflector apex, and a heatdeflecting shield member supported in said bulb at the front of the lead wire opening above the reflector axis and between said opening and said filament and substantially in a vertical plane transverse to said reflector axis to thereby break up and divert away from said one opening above the reflector axis the hot gaseous convection currents arising around said filament and thus prevent pocketing of the hot gas in said one opening.

2. A lamp as set forth in claim 1 wherein the said shield is secured to and supported by the lead wire extending through the said one opening which is located above the reflector axis.

3. An electric incandescent projector lamp comprising a sealed gas-filled bulb including a compact concave glass reflector section and a light-transmitting glass cover section and adapted for use with the reflector axis horizontal;

said reflector section having three lead wire openings arsaid reflector axis; metal thimble members at the exterior of said reflector section having their edges fused in the glass around the margins of respective said openings; first, second and third lead wires having their outer ends anchored in respective said thimbles and projecting through the associated first, second and third openings into the interior of said reflector section, and an auxiliary fourth lead wire connected at one end to the first lead wire and extending laterally, therefrom to the said vertical plane including the reflector axis at a point below said horizontal plane with its other free end in alignment with the third lead wire; a first coiled filament extending horizontally between and connected to said first and second lead wires; a second coiledfilament extending vertically between and connected to said third lead wire and to the said free end of said auxiliary fourth lead wire; said first horizontal and second vertical filaments being spaced apart along the reflector axis with the second vertical filament nearer to and relatively close to the apex of the reflector; and a heat-deflecting shield member supported from said third lead wire and extending downwardly therefrom in a vertical plane transverse to the reflector axis to be between said second vertical filament and the apex of the reflector and at the front of said third lead wire opening to thereby break up and divert away from said third lead wire opening the hot gaseous convection currents arising around said vertical filament and thus 6 avoid pocketing of the hot gas in said third lead wire opening.

References Cited STATES PATENTS UNITED 2,381,490 8/1945 Eitel et a1. 31342 2,515,337 7/1950 Clark et al 31343 X 2,791,714 5/1957 Beesley 313-115 2,973,443 2/1961 Wiley 313-42 3,283,198 11/1966 Bellott et a1 31342 X JAMES W. LAWRENCE, Primary Examiner. P. C. DEMEO, Assistant Examiner. 

1. AN ELECTRIC INCANDESCENT PROJECTOR LAMP COMPRISING A SEALED GAS-FILLED BULB INCLUDING A COMPACT CONCAVE GLASS REFLECTOR SECTION AND A LIGHT-TRANSMISSION GLASS COVER SECTION AND ADAPTED TO BE OPERATED WITH THE REFLECTOR AXIS HORIZONTAL, SAID REFLECTOR SECTION HAVING AT LEAST TWO LEAD WIRE OPENINGS ADJACENT ITS APEX WITH ONE OF SAID OPENINGS ABOVE SAID REFLECTOR AXIS SUBSTANTIALLY IN A VERTICAL PLANE INCLUDING SAID AXIS, METAL THIMBLE MEMBERS AT THE EXTERIOR OF SAID REFLECTOR SECTION CLOSING RESPECTIVE SAID OPENINGS AND HAVING THEIR EDGES FUSED IN THE GLASS AROUND THE MARGINS OF SAID OPENINGS, LEAD WIRE HAVING THEIR OUTER ENDS ANCHORED IN RESPECTIVE SAID THIMBLES AND EXTENDING THROUGH THE ASSOCIATED SAID OPENINGS INTO THE INTERIOR OF SAID REFLECTOR SECTION, A HIGH INTENSITY HELICALLY COILED FILAMENT IN SAID BULB ELECTRICALLY CONNECTED TO AND SUPPORTED FROM SAID LEAD WIRES TO EXTEND VERTICALLY SUBSTANTIALLY IN SAID VERTICAL PLANE INCLUDING SAID REFLECTOR AXIS AND RELATIVELY CLOSE TO SAID REFLECTOR APEX, AND A HEATDEFLECTING SHIELD MEMBER SUPPORTED IN SAID BULB AT THE FRONT OF THE LEAD WIRE OPENING ABOVE THE REFLECTOR AXIS AND 